Ventilated rotor hubs are used in electric fans to cool the components of the electric motor during operation. In particular, in fans for motor vehicle radiators, cooling of the electric motor is indispensable. They have to have a high operational reliability at highly varied temperatures, since at an increased temperature of the conductors, the resistance thereof and thus the power loss, which is in turn converted into heat, also increase, and this can lead to the destruction of the electric components and parts of the electric motor (in other words the control electronics, the power switch and the windings) and thus to the electric motor failing.
European patent EP 1 623 122 B1 discloses such a ventilated rotor hub of a motor vehicle fan. In this case, a hub of the fan wheel comprises ribs on the inside thereof which act as centrifugal fan blades. An airflow through the electric motor is thus provided and is drawn in from the pressure side of the fan, reversed inside the hub by the shape of the ribs, and blown out back to the pressure side. The hub further comprises, on the flat side thereof orientated towards the underpressure side, slits which are provided in the region of the ribs in a particular radius portion in such a way that an outer part of the hub is connected to an inner part of the hub exclusively via the ribs. This construction serves to influence the torsional oscillation behaviour of the rotor hub. An influence on the airflow by means of the slits is not disclosed.